Elastomers are useful as elastic nonwovens or films in applications ranging from diaper waistband, adult incontinence, personal hygiene and other applications. Most of these elastic closures are constructed with facing layers that include a nonwoven substrate that is plastic in properties and provides aesthetic attributes such as touch, feel. Examples of such include those disclosed in US 2008/0045917 and its counterparts. The plastic facing layers sandwich the elastic (core) layer, which is inherently elastomeric and possesses a rubbery feel that is not desirable for skin contact in the closure applications. The composite nonwoven or film laminate comprising the outer facing layer and the inner elastic layer is subjected to a mechanical activation step that serves to remove the plastic constraints imposed by the facing layer. During the mechanical activation step, the fabric is subjected to stretch at very high strain rates, and if the facing layer is not ductile, the fabric will tear or suffer mechanical damage in the process. It is thus important that the facing layer be extensible to survive this activation step.
Spunbond polypropylene nonwovens, although they possess desirable aesthetic properties, are not extensible and are unlikely to be effectively activated in the high speed stretch process when used as facing layers. The disclosure of U.S. Pat. No. 5,804,286 describes a highly extensible spunbond nonwoven fabric comprising an isotactic 76 wt % isotactic polypropylene, 20% propylene copolymer and 4% polyethylene. A spunbond fabric of the above composition is abrasion resistant and has a cross direction (CD) elongation of 190%. Owing to the high extensibility, such nonwovens can be effectively used as facing layers. However, a less complex composition that will survive mechanical activation and having high miscibility would be preferable.
We solve this and other problems by providing a nonwoven facing layer comprising polypropylene and a low ethylene content propylene-based elastomer, where the ethylene content of the elastomer provides miscibility with the polypropylene homopolymer or copolymer. These formulations have high elongation and extensibility.
Other relevant disclosures include U.S. Pat. No. 5,272,003, U.S. Pat. No. 5,366,782, U.S. Pat. No. 6,075,179, U.S. Pat. No. 6,342,565, U.S. Pat. No. 7,026,404, US 2008/0199673, US 2008/0182116, US 2008/0182940, US 2008/0182468, US 2006/0172647, US 2005/0130544, US 2005/0106978 and WO 2008/094337.